Yeah there does seem to be two variations on the Prime Directive.
At first, it's a matter of non-interference--seemingly regardless of the technological level. There were exceptions but TOS often showed Kirk introducing himself as captain of the Enterprise representing the Federation of Planets, even to "primitive natives". If that was over their heads, he'd talk about people coming from points of light in the sky and so on. The PD issues were about interfering, not much concern about revealing the fact of alien life and other worlds.
Later, mostly TNG-onward, the Prime Directive was equally about non-disclosure, not revealing the existance of other life and civilizations, the whole pre-warp argument.
Sure, disclosure of alien life can be a *kind* of interference. But back in TOS, it was mainly about non-interference. Freely talking about the Federation and all kinds of space aliens wasn't that taboo.
Unless non-interference and non-disclosure are subsets of a more lengthy and detailed General Order Number One.